This invention relates to air cleaners employing replaceable filter material, and particularly to an improved filter material support means therein for facilitating replacement of the filter material.
There are generally three basic means available for filtering the circulated air in domestic heating and cooling systems. One means is a throw-away filter positioned within the blower chamber of the furnace. Such a filter, generally made of fiber-glass, is relatively inefficient in removing contaminants from the circulating air. Such a filter, however, is the most widely used filtering means because it is quite inexpensive, easily replaceable, and requires no major mounting structure.
Another of the three basic filtering means is a highly-efficient electrostatic air cleaner which includes a cell comprising an ionizing grid and collector plates, and an electrical power supply for generating the high voltages required for the cell. Such a device is relatively expensive to purchase. Also, because of the device's physical size, a frame of some type must be installed in the air duct for supporting the cell. Additionally, provisions must be made for connecting the cell power supply to a source of electrical power. Thus, in addition to the initial purchase cost of the electrostatic air cleaner itself, there can be an appreciable installation cost.
The third of the three basic filtering means is a non-electric filter which has a considerably larger filtering surface than the above-described fiber-glass filter. Such a filter has an efficiency considerably higher than that of the conventional fiber-glass filter and somewhat less than that of the electrostatic air cleaner. Examples of such non-electric filter means are disclosed in U.S. Pat. Nos. 3,494,113 and 3,789,589.
The larger filtering surface in the non-electric filter is achieved by pleating the filter material. Because such pleating results in a filter that is physically thicker or wider than the conventional fiber-glass filter, such a pleated filter does not fit in the blower chamber of the furnace. Such a pleated filter, therefore, is generally mounted in the air duct. Even though both the pleated filter and the electrostatic air cleaner require modification of the air duct, the overall installed cost to the homeowner is less with the pleated filter arrangement than with the electrostatic air cleaner. Specifically, the purchase cost of the complete pleated filter assembly is less, and there are no electrical connections involved.
In the pleated filter arrangement, it is necessary to replace the filter material when it becomes excessively dirty. It is considered essential that the periodic filter replacement be relatively simple so as to be within the capability of a do-it-yourself homeowner.